DM can't add items or spells to a specific Character Sheet

So I ran into a strange little "bug". I'm hoping that I'm simply just overlooking a checked box or something. Anyway, I am running a campaign and the party just reacquired their lost items. I have re-added everyone's items to their character sheets via the ingame Compendium.... but here is the problem. For whatever reason, one of the character sheets, I'm unable to drag and drop from the compendium. All the others work like a charm but this one, nothing happens. I'm still able to manually edit the sheet but I'd rather not have to deal with manually adding weapons and spells because its kind of annoying. Am I missing something obvious? I feel like I am because I don't understand why this specific sheet doesn't work like the others that are in the same game. Its not like the settings are different... Idk Any help would be awesome!  Thanks! 

I'm curious as to what's causing this; when you find the answer, please give us an update here. No clue if this can possibly be the issue, but here's one thing to check: Does the character sheet in question share a name with another character sheet in the same game? (Do you have a PC named "Goblin", for example?) Does the name of the character contain any unusual symbols? If you make a copy of the character, does drag and drop work on the copy?

Also, make sure it is the only sheet open. Roll20 sometimes gets confused about which window to drop to. To make certain, be sure you have closed any minimized windows. (And of course, that the sheet is not popped out into its own window).

I have had this happen many times when I first started using roll20 and over time I developed a strict table rule where only one person is allowed to edit a sheet at a time, so whenever I, as the DM, need to do something with someones sheet, I order them to close their sheet entirely first.  Ever since I instituted this, the wonky drag and drop bug stopped showing up in my sessions.  As for how to fix it?  Sometimes it fixes when they do an update to the sheet you are actually using, but I've found that the most reliable fix is to remake the sheet entirely.  This is also why I backup my campaign characters after every session too.